Electrophotographic photoreceptor

ABSTRACT

Crystals of hydroxygallium phthalocyanine, a method of preparing the crystals, a photoconductive material containing the crystals, and an electrophotographic photoreceptor having the material. The photoreceptor has excellent electrophotographic characteristics. The crystals of hydroxygallium phthalocyanine have distinct diffraction peaks at (i) 7.5°, 9.9°, 12.5°, 16.3°, 18.6°, 25.1° and 28.3°, or (ii) 7.7°, 16.5°, 25.1° and 26.6°, or (iii) 7.9°, 16.5°, 24.4° and 27.6°, or (iv) 7.0°, 7.5°, 10.5°, 11.7°, 12.7°, 17.3°, 18.1°, 24.5°, 26.2° and 27.1°, or (v) 6.8°, 12.8°, 15.8° and 26.0° or (vi) 7.4°, 9.9°, 25.0°, 26.0°, and 28.2° of the Bragg angle (2θ±0.2) in the X-ray diffraction spectrum. The electrophotographic photoreceptor has a light-sensitive layer containing the photoconductive material of the crystals.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of application Ser. No. 07/873,026 filed on Apr. 24, 1992 now U.S. Pat. No. 5,302,479.

FIELD OF THE INVENTION

The present invention relates to crystals of hydroxygallium phthalocyanine useful as a photoconductive material, a method of preparing the crystals, a photoconductive material comprising the crystals, and an electrophotographic photoreceptor comprising the photoconductive material. The photoreceptor is, in one embodiment, composed of a charge generating material and a binder resin.

BACKGROUND OF THE INVENTION

Phthalocyanine compounds are useful as materials for paint compositions, printing inks and catalysts and as electronic materials and, in particular, they have been broadly investigated as materials for electrophotographic photoreceptors, materials for optical recording and materials for photo-electric conversion in these days.

Regarding electrophotographic photoreceptors, recently, the demand for extending the light-sensitive wavelength range of organic photoconductive materials which have heretofore been proposed up to the near infrared wavelength range of semiconductor lasers (780 to 830 nm) so as to use the materials as a photoreceptor for a digital recording system such as a laser printer. From the viewpoint, squalilium compounds (as disclosed, e.g., in JPA-49-105536 and JP-A-58-21414, triphenylamine trisazo compounds (as disclosed, e.g., in JP-A-61-151659) and phthalocyanine compounds (as disclosed, e.g., in JP-A-48-34189 and JP-A-57-148745) have been proposed as photoconductive materials for semiconductor lasers. (the term "JP-A" as used herein means an "unexamined published Japanese patent application")

Where organic photoconductive materials are used as light-sensitive materials for semiconductor lasers, they are needed to satisfy the conditions that the light-sensitive wavelength range is extended up to a long wavelength range and that the sensitivity and durability of the photoreceptors to be formed therefrom are good. The above-mentioned organic photoconductive materials do not sufficiently meet the conditions.

In order to overcome various drawbacks of the known photoconductive materials, the materials have been investigated with respect to the relationship between the crystal form and the electrophotographic characteristics. In particular, many reports relating to phthalocyanine compounds have heretofore been disclosed.

In general, it is known that phthalocyanine compounds have various crystal forms, depending upon the difference in the manufacture method and treating method, and that the difference in the crystal form has a great influence on the photo-electric conversion characteristics of phthalocyanine compounds. Regarding crystal forms of phthalocyanine compounds, for example, with respect to copper phthalocyanine, various crystal forms of α, π, χ, ρ, γ, and δ are known in addition to a stable crystal form of β. It is also known that these crystal forms are mutually transferable to each other by mechanical strain force, sulfuric acid treatment, organic solvent treatment or heat treatment (as described, e.g., in U.S. Pat. Nos. 2,770,029, 3,160,635, 3,708,292 and 3,357,989). JP-A-50-38543 describes the relationship between the difference of crystal forms of copper phthalocyanine and the electrophotographic characteristics of them.

Regarding the relationship between the crystal forms of hydroxygallium phthalocyanine and the electrophotographic characteristics of them, JP-A-1-221459 mentions crystals obtained by an acid-pasting method.

However, not only the above-mentioned hydroxygallium phthalocyanine crystals but also phthalocyanine compounds which have heretofore been proposed are not sufficient in point of the light sensitivity and the durability when used as a light-sensitive material.

In addition, when hydroxyallium phthalocyanine crystals are used in the form of a dispersion in a binder resin, the crystals are inferior in the dispersibility and the coatability of the dispersion. Where the crystals are used as a photoreceptor, they have problems on the light-sensitivity and the charge retentiveness. Further, they often cause drawbacks of fog or black spots in images formed. Thus, the crystals do not have sufficient characteristics.

Therefore, development of novel crystals of phthalocyanine compounds, which have improved characteristics of light sensitivity, durability, charge retentiveness, coatability and image quality with still having the intrinsic favorable characteristics of the compounds of themselves as a photoconductive material, has been desired.

The present invention has been made in view of the above-mentioned situation.

SUMMARY OF THE INVENTION

One object of the present invention is to provide novel crystals of hydroxygallium phthalocyanine.

Another object of the present invention is to provide a photoconductive material which comprises novel crystals of hydroxygallium phthalocyanine and has excellent light sensitivity and durability.

Further object of the present invention is to provide an electrophotographic photoreceptor having high sensitivity characteristics and good charge retentiveness to cause few image defects, the coatability of the photoconductive material on a support in preparing the photoreceptor being improved.

As a result of earnest investigations, the present inventors have found that novel crystals of hydroxygallium phthalocyanine having high sensitivity and durability as a photoconductive material can be obtained by applying particular treatment to hydroxygallium phthalocyanine as obtained by synthesis. The inventors further have found that an electrophotographic photoreceptor having the novel crystals and a particular binder resin in the light-sensitive layer has much improved light-sensitive characteristics and charge-retaining characteristics, that the dispersibility of the crystals in the resin as well as the coatability of the dispersion for forming the light-sensitive layer is good and that the photoreceptor causes few image defects. On the basis of the finings, they have completed the present invention.

Accordingly, the present invention provides crystals of hydroxygallium phthalocyanine having distinct diffraction peaks at the particular angles of the Bragg angle (2θ±0.2) in the X-ray diffraction spectrum. The particular angles are selected from the following (i) to (v): (i) 7.5°, 9.9°, 12.5°, 16.3°, 18.6°, 25.1° and 28.3°; (ii) 7.7°, 16.5°, 25.1° and 26.6°; (iii) 7.9°, 16.5°, 24.4° and 27.6°; (iv) 7.0°, 7.5°, 10.5°, 11.7°, 12.7°, 17.3°, 18.1°, 24.5°, 26.2° and 27.1°; (v) 6.8°, 12.8°, 15.8° and 26.0°; and (vi) 7.4°, 9.9°, 25.0°, 26.0° and 28.2°.

The present invention also provides a method of preparing hydroxygallium phthalocyanine crystals having distinct diffraction peaks at the particular angles (i) of the Bragg angle (2θ=0.2) in the X-ray diffraction spectrum. The method comprises treating hydroxygallium phthalocyanine with a solvent containing at least one selected from the group consisting of amides, esters and ketones.

The present invention also provides a photoconductive material for electrophotographic photoreceptor comprising at least one of the above-mentioned hydroxygallium phthalocyanine crystals having distinct diffraction peaks at the particular angles (i) to (v) of the Bragg angle (2θ±0.2) in the X-ray diffraction spectrum.

The present invention further provides an electrophotographic photoreceptor comprising an electroconductive support having thereon a light-sensitive layer containing at least one of the above-mentioned hydroxygallium phthalocyanine crystals having distinct diffraction peaks at the particular angles (i) to (v) of the Bragg angle (2θ±0.2) in the X-ray diffraction spectrum.

In a preferred embodiment the light-sensitive layer of the photoreceptor has a laminate structure comprising a charge generating layer and a charge transporting layer as laminated in this order on the support, and the charge generating layer contains the hydroxygallium phthalocyanine crystals and a binder resin comprising at least one selected from polyvinyl acetal resins, vinyl chloride-vinyl acetate copolymers, phenoxy resins and modified ether type polyester resins.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of showing an embodiment of the electrophotographic photoreceptor of the present invention.

FIG. 2 is a schematic sectional view of showing another embodiment of the electrophotographic photoreceptor of the present invention.

FIG. 3 is a schematic sectional view of showing still another embodiment of the electrophotographic photoreceptor of the present invention.

FIG. 4 is a schematic sectional view of showing still another embodiment of the electrophotographic photoreceptor of the present invention.

FIG. 5 is a powder X-ray diffraction pattern of hydroxygallium phthalocyanine crystals obtained in Synthesis Example 1.

FIG. 6 is an infrared spectrum pattern of hydroxygallium phthalocyanine crystals obtained in Synthesis Example 1.

FIG. 7 is a powder X-ray diffraction pattern of hydroxygallium phthalocyanine crystals obtained in Synthesis Example 2.

FIG. 8 is a powder X-ray diffraction pattern of hydroxygallium phthalocyanine crystals obtained in Example 1.

FIG. 9 is an infrared spectrum pattern of hydroxygallium phthalocyanine crystals obtained in Example 1.

FIG. 10 is a powder X-ray diffraction pattern of hydroxygallium phthalocyanine crystals obtained in Example 2.

FIG. 11 is a powder X-ray diffraction pattern hydroxygallium phthalocyanine crystals obtained in Example 3.

FIG. 12 is a powder X-ray diffraction pattern of hydroxygallium phthalocyanine crystals obtained in Example 4.

FIG. 13 is a powder X-ray diffraction pattern of hydroxygallium phthalocyanine crystals obtained in Example 5.

FIG. 14 is a powder X-ray diffraction pattern of hydroxygallium phthalocyanine crystals obtained in Example 6.

FIG. 15 is a powder X-ray diffraction pattern of hydroxygallium phthalocyanine crystals obtained in Example 8.

FIG. 16 is a powder X-ray diffraction pattern of hydroxygallium phthalocyanine crystals obtained in Example 10.

FIG. 17 is a powder X-ray diffraction pattern of hydroxygallium phthalocyanine crystals obtained in Example 11.

FIG. 18 is a powder X-ray diffraction pattern of hydroxygallium phthalocyanine crystals obtained in Example 33.

FIG. 19 is a visible-infrared spectrum pattern of hydroxygallium phthalocyanine crystals obtained in Example 33.

FIG. 20 is a visible-infrared spectrum pattern of hydroxygallium phthalocyanine crystal obtained in Example 1.

DETAILED DESCRIPTION OF THE INVENTION

Hydroxygallium phthalocyanines of the present invention are represented by a general formula (I): ##STR1## where R1, R2, R3 and R4 each represent a halogen atom or an aliphatic alkoxy group having from 1 to 5 carbon atoms; and k, l, m and n each represents an integer of from 0 to 4.

In the present invention, the X-ray diffraction pattern is the measurement results of intensities of the Bragg angle (2θ) with respect to CuK.sub.α characteristic X-ray (wavelength: 1.541 Å). The measurement conditions are as follows:

Apparatus: X-ray diffractiometer (RAD-RC produced by Rigaku K.K.)

Target: Cu (1.54050 Å)

Voltage: 40.0 KV

Start angle: 5.00 deg

Stop angle: 40.00 deg

Step angle: 0.020 deg

Hydroxygallium phthalocyanine crystals of the present invention are novel and are useful as a photoconductive materials, and they can be produced in the manner mentioned below for example.

Chlorogallium phthalocyanine produced by known methods is subjected to hydrolysis in an acid or alkaline solution or to acid-pasting so as to produce a hydroxygallium phthalocyanine. Alternatively, hydroxygallium phthalocyanine can be obtained in such a manner that a solution obtained by dissolving chloroindium phthalocyanine in conc. sulfuric acid is poured into water, and the resulting mixture is neutralized with ammonia to obtain hydroxyindium phthalocyanine (as disclosed in Bull. Soc. Chim. France, 1962, pp. 23-26 (1962)). The resulting hydroxygallium phthalocyanine crystals are directly treated with a solvent, or they are amorphatized by acid-pasting or mechanically milled in a ball mill, mortar, sand mill, kneader or attritor, and then treated with a solvent, to obtain the intended hydroxygallium phthalocyanine crystals of the present invention. If desired, a grinding aid such as sodium chloride or Glauber's salt may be used during grinding. The proportion of the grinding aid to the hydroxygallium phthalocyanine crystals to be ground is generally from 0.5/1 to 20/1, and preferably from 1/1 to 10/1. By using the grinding aid, the starting crystals can be transferred into crystals with a uniform crystal form extremely efficiently.

Crystal forms of hydroxygallium phthalocyanine crystals of the present invention vary depending on the kind of the above-mentioned treating conditions. Examples of the solvents used in the above solvent treatment include the following compounds:

(i) Examples of the solvents used for preparing hydroxygallium phthalocyanine crystals having distinct diffraction peaks at 7.5°, 9.9°, 12.5°, 16.3°, 18.6°, 25.1° and 28.3° of the Bragg angle (2θ±0.2) in the X-ray diffraction spectrum pattern include amides (e.g., N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone), esters (e.g., ethyl acetate, n-butyl acetate, iso-amyl acetate), and ketones (e.g., acetone, methyl ethyl ketone, methyl iso-butyl ketone).

(ii) Examples of the solvents used for preparing hydroxygallium phthalocyanine crystals having distinct diffraction peaks at 7.7°, 16.5°, 25.1° and 26.6° of the Bragg angle (2θ±0.2) in the X-ray diffraction spectrum pattern include alcohols (e.g., methanol, ethanol), and aromatic compounds (e.g., toluene, chlorobenzene).

(iii) Examples of the solvents used for preparing hydroxygallium phthalocyanine crystals having distinct diffraction peaks at 7.9°, 16.5°, 24.4° and 27.6° of the Bragg angle (2θ±0.2) in the X-ray diffraction spectrum pattern include organic amines (e.g., pyridine, piperidine), and sulfoxides (e.g., dimethylsulfoxide).

(iv) Examples of the solvents used for preparing hydroxygallium phthalocyanine crystals having distinct diffraction peaks at 7.0°, 7.5°, 10.5°, 11.7°, 12.7°, 17.3°, 18.1°, 24.5°, 26.2° and 27.1° of the Bragg angle (2θ±0.2) in the X-ray diffraction spectrum pattern include aromatic alcohols (e.g., benzyl alcohol).

(v) Examples of the solvents used for preparing hydroxygallium phthalocyanine crystals having distinct diffraction peaks at 6.8°, 12.8°, 15.8° and 26.0° of the Bragg angle (2θ±0.2) in the X-ray diffraction spectrum pattern include polyhydric alcohols (e.g., ethylene glycol, glycerin, polyethylene glycol).

(vi) Examples of the solvents used for preparing hydroxygallium phthalocyanine crystals having distinct diffraction peaks at 7.4°, 9.9°, 25.0°, 26.0°, and 28.2° of the Bragg angle (2θ±0.2) in the X-ray diffraction spectrum pattern include amides (e.g., N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone), esters (e.g., ethyl acetate, n-butyl acetate, iso-amyl acetate), and ketones (e.g., acetone, methyl ethyl ketone, methyl iso-butyl ketone).

The solvent to be used in preparing the above-mentioned hydroxygallium phthalocyanine crystals may be in the form of a mixed solvent comprising two or more different solvents or an aqueous mixed solvent comprising one or more different solvents and water.

In accordance with the present invention, a hydroxygallium phthalocyanine is brought into contact with the prescribed solvent to prepare the above-mentioned hydroxygallium phthalocyanine crystals having distinct diffraction peaks at the particular Bragg angles in an X-ray diffraction spectrum pattern. Such solvent treatment includes, for example, not only ordinary recrystallization treatment, but also treatment of a hydroxygallium phthalocyanine, which has been treated with an ordinary organic solvent for a purification during or after synthesis thereof, by washing or wet-grinding with the prescribed solvent. Specifically, in order to prepare hydroxygallium phthalocyanine crystals having the determined crystal form, hydroxygallium phthalocyanine is subjected to solvent treatment by at least one of these treating methods. If any other organic solvents than those defined in the above-mentioned (i) to (vi) are used for washing or wet-grinding treatment of hydroxygallium phthalocyanine, crystal transfer into the desired hydroxygallium phthalocyanine crystals each with the determined crystal form of anyone of (i) to (vi) may sometimes be impossible.

Regarding the solvent treatment conditions, the amount of the solvent used is generally from 1 to 200 parts, and preferably from 10 to 100 parts, per one part of hydroxygallium phthalocyanine to be treated therewith; and the treating temperature is generally from 0° to 150° C., and preferably from room temperature to 100° C. The solvent treatment may be effected in an appropriate vessels under static condition or with stirring. Wet grinding in a ball mill, a mortar, a sand mill, a kneader or an attritor may be effected with the determined solvent. In grinding, inorganic compounds such as sodium chloride or Glauber's salt as well as grinding media such as glass beads, steel beads or alumina beads can be used.

By the above-mentioned solvent treatment, the crystals of hydroxygallium phthalocyanine of the present invention advantageously having better crystallinity and having a more uniform grain size distribution can be obtained.

The present invention also provides an electrophotographic photoreceptor, which has the above-mentioned hydroxygallium phthalocyanine crystals to be obtained by the above-mentioned solvent treatment, as the photoconductive material in the light-sensitive layer.

In the photographic photoreceptor of the present invention, the light-sensitive layer may be a single layer or may have a laminated structure composed of a charge generating layer and a charge transporting layer each having a different function. In the latter case, the charge generating layer is composed of the above-mentioned hydroxygallium phthalocyanine crystals and a binder resin.

FIG. 1 to FIG. 4 are schematic sectional views showing embodiments of the electrophotographic photoreceptor of the present invention. In the embodiment shown in FIG. 1, a light-sensitive layer composed of charge generating layer 1 and charge transporting layer 2 as laminated thereover, is coated over electroconductive support 3. In the embodiment shown in FIG. 2, subbing layer 4 is provided between charge generating layer 1 and electroconductive support 3. In the embodiment shown in FIG. 3, protective layer 5 is coated over the light-sensitive layer. In the embodiment shown in FIG. 4, the photoreceptor has both subbing layer 4 and protective layer 5.

These layers 1 to 5 will be explained in detail hereunder, along with a light-sensitive layer with a single layer constitution.

Charge generating layer 1 of the electrophotographic photoreceptor of the present invention can be formed by preparing a coating composition of a dispersion of the above-mentioned hydroxygallium phthalocyanine crystals dispersed in a solution of a binder resin dissolved in an organic solvent, followed by coating the composition onto electroconductive support 3.

The binder resin used in charge generating layer 1 may be selected from various resins of a broad range. Examples thereof include insulating resins, such as polyvinyl acetal resins (e.g., polyvinyl butyral resins, polyvinyl formal resins, and partially acetallized polyvinyl butyral resins in which a part of the butyral moiety has been modified with formal or acetacetal), polyarylate resins (e.g., polycondensate of hisphenol A and phthalic acid), polycarbonate resins, polyester resins, modified ether type polyester resins, phenoxy resins, polyvinyl chloride resins, polyvinylidene chloride resins, polyvinyl acetate resins, polystyrene resins, acrylic resins, methacrylic resins, polyacrylamide resins, polyamide resins, polyvinyl pyrimidine resins, cellulosic resins, polyurethane resins, epoxy resins, silicone resins, polyvinyl alcohol resins, polyvinyl pyrrolidone resins, casein, vinyl chloride-vinyl acetate type copolymers (e.g., vinyl chloride-vinyl acetate copolymer, hydroxyl-modified vinyl chloride-vinyl acetate copolymer, carboxy-modified vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer), styrene-butadiene copolymers, vinylidene chloride-acrylonitrile copolymers, styrene-alkyd resins, silicone-alkyd resins, and phenol-formaldehyde resins. In addition, organic photoconductive polymers such as poly-N-vinyl carbazole, polyvinyl anthracene and polyvinyl pyrene can also be used. However, these insulating resins and organic photoconductive polymers are not limitative. These binder resins can be used singly or in combination of two or more of them.

As the solvent of dissolving the binder resin, preferred is an organic solvent which does not dissolve subbing layer 4. Specific examples of the organic solvents include alcohols such as methanol, ethanol, n-propanol, i-propanol, n-butanol and benzyl alcohol; ketones such as acetone, methyl ethyl ketone and cyclohexanone; amides such as dimethylformamide and dimethylacetamide; sulfoxides such as dimethylsulfoxide; cyclic or linear ethers such as tetrahydrofuran, dioxane, diethyl ether, methyl cellosolve and ethyl cellosolve; ester such as methyl acetate, ethyl acetate and n-butyl acetate; halogenated aliphatic hydrocarbons such as methylene chloride, chloroform, carbon tetrachloride, dichloroethylene and trichloroethylene; mineral oils such as ligroin; aromatic hydrocarbons such as benzene, toluene and xylene; and halogenated aromatic hydrocarbons such as chlorobenzene and dichlorobenzene. These can be used singly or in combination of two or more of them.

The proportion of the above-mentioned hydroxygallium phthalocyanine crystals to the binder resin generally falls within the range of from 40/1 to 1/20, and preferably from 10/1 to 1/10, by weight. If the proportion of the hydroxygallium phthalocyanine crystals is too high, the stability of the coating composition tends to lower. If it is too low, the sensitivity of the photoreceptor tends to lower. Therefore, the proportion generally falls within the above range.

For dispersing the hydroxygallium phthalocyanine crystals, any ordinary methods, such as ball mill dispersion method, attritor dispersion method or sand mill dispersion method, can be employed. The crystals are preferred to be dispersed finely to have a grain size of 0.5 μm or less, more preferably 0.3 μm or less, and particularly preferably 0.15 μm or less. In dispersing the crystals, such a condition is needed that the crystal form of the hydroxygallium phthalocyanine crystals to be dispersed does not change. In this connection, the present inventors confirmed that the crystal forms of the hydroxygallium phthalocyanine crystals of the present invention do not change after dispersion by employing any of the above-mentioned dispersion methods.

For coating the coating composition, any conventional method may be employed, such as dip coating method, spray coating method, spinner coating method, bead coating method, wire bar coating method, blade coating method, roller coating method, air knife coating method or curtain coating method. Drying of the coated composition may be effected preferably by drying to touch at room temperature followed by drying with heat under static condition or with blowing at a temperature of from 30° to 200° C. for a period of from 5 minutes to 2 hours. The thickness of charge generating layer 1 is generally from 0.05 to 5 μm, and preferably from 0.2 to 2.0 μm.

In charge generating layer 1, the hydroxygallium phthalocyanine crystals of the present invention having distinct diffraction peaks at 7.5°, 9.9°, 12.5°, 16.3°, 18.6°, 25.1° and 28.3° of the Bragg angle (2θ±0.2°) in the X-ray diffraction spectrum pattern are preferably selected from the viewpoints of the light-sensitivity and durability. Of the above-mentioned binder resins, at least one selected from polyvinyl acetal resins, vinyl chloride-vinyl acetate copolymers, phenoxy resins and modified ether type polyester resins are preferred from the viewpoints of the dispersibility of hydroxygallium phthalocyanine crystals therein, the coatability of the resulting dispersion as a coating composition and the sensitivity characteristics, charge retentiveness and image characteristics of the photoreceptor formed with the coating composition. The combination of hydroxygallium phthalocyanine crystals of the present invention having distinct diffraction peaks at 7.5°, 9.9°, 12.5°, 16.3°, 18.6°, 25.1° and 28.3° of the Bragg angle (2θ±0.2°) in the X-ray diffraction spectrum pattern and these binder resins are favorable since the photographic characteristics of the electrophotographic photoreceptor to be manufactured are especially excellent.

Charge transporting layer 2 of the electrophotographic photoreceptor of the present invention may be formed by incorporating a charge transporting material into a binder.

As the charge transporting material, any known charge transporting materials can be used, for example, oxadiazole derivatives such as 2,5-bis-(p-diethylaminophenyl)-1,3,4-oxadiazole; pyrazoline derivatives such as 1,3,5-triphenylpyrazoline and 1-pyridyl-(2)]-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline; aromatic tertiary monoamino compounds such as triphenylamine and dibenzylaniline; aromatic tertiary diamino compounds such as N,N'-diphenyl-N,N'-bis(m-tolyl)benzidine; 1,2,4-triazine derivatives such as 3-(p-diethylaminophenyl)-5,6-di-(p-methoxyphenyl)-1,2,4-triazine; hydrazone derivatives such as 4-diethylaminobenzaldehyde-2,2-diphenylhydrazone; quinazoline derivatives such as 2-phenyl-4styrylquinazoline; benzofuran derivatives such as 6-hydroxy-2,3-di-(p-methoxyphenyl)benzofuran; α-stilbene derivatives such as p-(2,2-diphenylvinyl)-N,N-diphenylaniline; triphenylmethane derivatives; enamine derivatives as described in Journal of Imaging Science, vol. 29, p. 7-10 (1985); carbazole, N-ethylcarbazole, poly-N-vinyl carbazole, halogenated poly-N-vinyl carbazoles, polyglycidyl carbazole, poly-γ-carbazole ethyl glutamate and their derivatives; polycyclic aromatic compounds such as anthracene, pyrene and phenanthrene; nitrogen-containing heterocyclic compounds such as indole and imidazole; and polyvinyl anthracene, poly-9-vinylphenyl anthracene, polyvinyl pyrene, polyvinyl acridine, polyvinyl acenaphthene, pyrene-formaldehyde resins, and ethylcarbazole-formaldehyde resins. However, these are not limitative. These charge transporting materials can be used either singly or in combination of two or more of them. Where a photoconductive polymer is used as the charge transporting material, it may form a layer by itself.

The charge transporting material to be used preferably includes benzidine compounds represented by formula (II): ##STR2## wherein R₅ represents a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom; R₆ and R₇ each represent a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, or a substituted amino group; and p and q each represent 0, 1 or 2,

and tetraaryl-m-phenylenediamine compounds represented by formula (III): ##STR3## wherein R₆, R₉, and R₁₀ each represent a hydrogen atom, an alkyl group, an alkoxy group, a substituted or unsubstituted aryl group or an aralkyl group.

Of the benzidine compounds of formula (II), more preferred are those represented by formula (IV) or (V) shown below for their high solubility in solvents and high compatibility with resins to form a uniform coating film with a uniform interface thereby providing an electrophotographic photoreceptor having high sensitivity and excellent stability against repeated use: ##STR4## wherein R₁₁ and R₁₂ each represent a hydrogen atom or a methyl group; ##STR5## wherein either one of R₁₃ and R₁₄ represents an alkyl group having 2 or more carbon atoms, with the other representing a hydrogen atom, an alkyl group, an alkoxy group or a substituted amino group.

As the binder resin of forming charge transporting layer 2, those mentioned above for charge generating layer can be used, for example, polycarbonate resins, polyester resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl acetate resins, styrene-butadiene copolymers, vinylidene chloride-acrylonitrile copolymers, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate-maleic anhydride copolymers, silicone resins, silicone-alkyd resins, phenol-formaldehyde resins, styrene-alkyd resins, and poly-N-vinylcarbazole resins.

Among the binder resins which can be used in the charge transporting layer, polycarbonate resins comprising a repeating unit represented by formulae (VI) to (XII) shown below are preferred since they exhibit particularly satisfactory characteristics: ##STR6##

The above-mentioned binder resins may be used either individually or in combination of two or more thereof.

Charge transporting layer 2 can be formed by preparing a coating composition from the above-mentioned charge transporting material and the binder resin and an organic solvent such as those mentioned above for charge generating layer 1, followed by coating the resulting coating composition onto charge generating layer 1 by the same means as the above-mentioned coating means. The proportion of the charge transporting material to the binder resin is preferably from 10/1 to 1/5 by weight. The thickness of charge transporting layer 2 is generally approximately from 5 to 50 μm, and preferably from 10 to 30 μm.

Where the light-sensitive layer of the photoreceptor of the present invention has a single layer constitution, the light-sensitive layer is a photoconductive layer comprising the above-mentioned hydroxygallium phthalocyanine crystals as dispersed in a charge transporting material and a binder resin. As the charge transporting material and binder resin, those to be used in preparing a laminate-structure light-sensitive layer can be used. The single-layer photoconductive layer may be formed in the same manner as mentioned above. Use of hydroxygallium phthalocyanine crystals having distinct diffraction peaks at 7.5°, 9.9°, 12.5°, 16.3°, 18.6°, 25.1° and 28.3° of the Bragg angle (2θ±0.2°) in the X-ray diffraction spectrum pattern and at least one binder resin selected from polyvinyl acetal resins, vinyl chloride-vinyl acetate copolymers phenoxy resins, modified ether type polyester resins, polycarbonate resins, polyester resins, and polystyrene resins is the most preferred because of the same reasons as mentioned above.

Where the light-sensitive layer is has a single layer constitution, the proportion of the charge transporting material to the binder resin is preferably be approximately from 1/20 to 5/1 by weight; and the proportion of the hydroxygallium phthalocyanine crystals to the charge transporting material is preferably approximately from 1/10 to 10/1 by weight.

As the electroconductive support 3, any conventional materials for preparing electrophotographic photoreceptors can be employed.

Specific examples thereof include metals such as aluminium, nickel, chromium and stainless steel; plastic films as coated with aluminium, titanium, nickel, chromium, stainless steel, gold, vanadium, tin oxide, indium oxide or ITO; as well as plastic films or paper coated with or dipped in an electroconductivity imparting agent. Electroconductive support 3 can be used in any shape such as a drum, sheet or plate support, which, however, is not limitative. If desired, the surface of electroconductive support 3 may be subjected to various treatment as long as the treatment would not have any adverse influence on the resulting image quality. For instance, the surface may be oxidized, treated with chemicals, colored or matted for making the surface diffusively reflectable.

In the present invention, subbing layer 4 may be provided between electroconductive support 3 and the light-sensitive layer. Subbing layer 4 is effective for inhibiting injection of any unnecessary charges from electroconductive support 3 to the light-sensitive layer while the layer is charged, and it has a function of improving the charging property of the light-sensitive layer. In addition, it also has another function of elevating the adhesiveness between the light-sensitive layer and electroconductive support 3. Furthermore, may also have a function of preventing light reflected from electroconductive support 3.

Examples of materials of forming subbing layer 4 include polyethylene resins, polypropylene resins, acrylic resins, methacrylic resins, vinyl chloride resins, vinylidene chloride resins, vinyl acetate resins, phenolic resins, polycarbonate resins, polyurethane resins, polyamide resins, polyimide resins, polyvinyl acetal resins, vinyl chloride-vinyl acetate copolymers, polyvinyl alcohol resins, polyacrylic acid resins, polyacrylamide resins, polyvinyl pyrrolidone resins, polyvinyl pyridine resins, water-soluble polyester resins, cellulose ester resins such as nitrocellulose, cellulose ether resins, caseins, gelatins, polyglutamic acids, starches, starch acetates, amino starches, organic zirconium compounds such as zirconium chelate compounds and zirconium alkoxide compounds, organic titanyl compounds such as titanyl chelate compounds and titanyl alkoxide compounds, and silane coupling agents.

The subbing layer is preferably formed mainly of an organometallic compound and a silane coupling agent. The subbing layer may further contain a binder resin compatible with the organometallic compound and silane coupling agent.

The organometallic compounds which can be used in the present invention are illustrated below according to the valence of the metal.

Compounds containing a tetravalent metal include zirconium chelate compounds, such as

tetraacetylacetonatozirconium,

butoxybisacetylacetonatozirconium,

tributoxyacetylacetonatozirconium,

tetrakis(ethyl acetoacetato)zirconium,

butoxytris(ethyl acetoacetato)zirconium,

tributoxymono(ethyl acetoacetato)zirconium,

dibutoxybis(ethyl lactato)zirconium,

bisacetylacetonatobis(ethyl acetoacetato)zirconium,

monoacetylacetonatotris (ethyl acetoacetato) zirconium, and bisacetylacetonatobis (ethyl lactato) zirconium; and zirconium alkoxides, such as zirconium n-butoxide and zirconium n-propoxide.

Titanium compounds include titanium ortho-titanic acid esters represented by formula (XIV): ##STR7## wherein R₁₅, R₁₆, R₁₇, and R₁₈ each represent a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a cresyl group, a stearyl group, a hexyl group, a nonyl group or acetyl group; poly-ortho-titanic acid esters represented by formula (XV): ##STR8## wherein R₁₉, R₂₀, R₂₁, and R₂₂ each represent a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a cresyl group, a stearyl group, a hexyl group, a nonyl group or a cetyl group; and r represents an integer of from 2 to 10; and titanium chelate compounds represented by formula (XVI):

    Ti(L).sub.s X.sub.1-s                                      (XVI)

wherein L represents a chelating group; X represents an ester group; and s represents 1 to 4, in which the ligands include a β-ketone, e.g., octylene glycol or acetylacetone; a hydroxycarboxylic acid, e.g., lactic acid, malic acid, tartaric acid or salicylic acid; a keto-ester, e.g., acetoacetic ester, and a keto-alcohol, e.g., diacetone alcohol.

Compounds having a trivalent metal include aluminum alkoxides, such as aluminum isopropoxide, aluminum mono-sec-butoxydiisopropoxide, aluminum sec-butoxide, and aluminum ethoxide; aluminum chelate compounds, such as diisopropoxy(ethyl acetoacetato)aluminum, tris(ethyl acetoacetato)aluminum, tris(acetylacetonato)aluminum, and bis(ethyl acetoacetato)monoacetylacetonatoaluminum; indium alkoxides, such as indiummethoxide, indium ethoxide, indium isopropoxide, and indium n-butoxide; antimony alkoxides, such as antimony methoxide, antimony ethoxide, antimony isopropoxide, and antimony n-butoxide; and boron alkoxides, such as boron methoxide and boron n-butoxide.

Compounds having a divalent metal include bis(acetylacetonato)manganese (II), bis(acetylacetonato)zinc (II), and bis(acetylacetonato)tin (II).

The silane coupling agents which can be used in the present invention include vinyltrichlorosilane, vinyltriethoxysilane, vinyltris(β-methoxyethoxy)silane,

γ-glycidoxypropyltrimethoxysilane,

γ-methacryloxypropyltrimethoxysilane,

γ-aminopropylmethyldimethoxysilane,

γ-chloropropyltrimethoxysilane,

γ-mercaptopropyltrimethoxysilane,

γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane,

methyltrimethoxysilane, dimethyldimethoxysilane,

trimethylmonomethoxysilane, diphenyldimethoxysilane,

diphenyldiethoxysilane, monophenyltrimethoxysilane,

γ-(2-aminoethyl)aminopropyltrimethoxysilane,

γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, and

γ-methacryloxypropyltrimethoxysilane.

The binder resins which can be used in the subbing layer of the present invention include polyurethane resins, polyvinyl butyral resins, polyvinyl formal resins, and polyvinyl acetate resins.

The subbing layer contains at least one of the above-mentioned organometallic compounds and at least one of the above-mentioned silane coupling agents and, if desired, at least one of the above-mentioned binder resins. The organometallic compounds, silane coupling agents and binder resins may be each used in combination of two or more thereof. The amount of the silane coupling agent may be selected arbitrarily from the range of from 5 to 95% by weight based on the organometallic compound.

The amount of the binder resin, if used, should be not higher than 25% by weight based on the total weight of the organometallic compound and silane coupling agent. If it exceeds 25% by weight, the coating composition is liable to gelation and, besides, deterioration of electrophotographic characteristics of the resulting photoreceptor, particularly a reduction in sensitivity and an increase in residual potential in a low temperature and low humidity condition, would result. If the film thickness is increased with the amount of the binder resin being less than 5% by weight, the subbing layer tends to suffer from cracks after film formation. Accordingly, the binder resin is preferably used in an amount ranging from 5 to 25% by weight.

The subbing layer usually has a thickness of from 0.1 to 10 μm, and preferably from 0.1 to 2 μm.

The subbing layer can be formed by coating a solution of the above-described materials in a solvent on a conductive support in a usual coating method, such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating or curtain coating, and drying in a temperature between 100° and 200° C.

In the present invention, the surface of the light-sensitive layer may be coated with protective layer 5 if desired. Protective layer 5 is formed for the purpose of preventing chemical deterioration of charge transporting layer 2 during charging of the laminate-structure light-sensitive layer and of improving the mechanical strength of the light-sensitive layer.

Protective layer 5 can be formed by incorporating an electroconductive material in a binder resin. Examples of the electroconductive material include metallocene compounds such as dimethylferrocene; aromatic amino compounds such as N,N'-diphenyl-N,N'-bis-(m-tolyl)benzidine; and metal oxides such as antimony oxide, tin oxide, titanium oxide, indium oxide, and tin oxide-antimony oxide. However, these are not limitative. As the binder resin, any conventional binder resin can be used. Examples thereof include polyamide resins, polyurethane resins, polyester resins, epoxy resins, polyketone resins, polycarbonate resins, polyvinyl ketone resins, polystyrene resins, and polyacrylamide resins.

Protective layer 5 is preferably to have an electric resistance of from 10⁹ to 10¹⁴ Ω.cm. If the electric resistance of the layer is more than 10¹⁴ Ω.cm, the residual potential tends to rise to give images with much fog. If it is less than 10⁹ Ω.cm, the images to be formed tends to be blurred and the resolving power would lower. The protective layer must be formed in such a way that it does not substantially interfere with penetration of the light therethrough as irradiated thereto for imagewise exposure.

For forming protective layer 5, any conventional coating methods may be employed. Examples thereof include blade coating method, wire bar coating method, spray coating method, dip coating method, bead coating method, air knife coating method, and curtain coating method. The thickness of protective layer 5 is generally from 0.5 to 20 μm, and preferably from 1 to 10 μm.

The present invention will be explained in more detail by way of the following examples, which, however, are not intended to restrict the scope of the present invention. Unless otherwise specifically defined, all "parts" therein are by weight.

SYNTHESIS EXAMPLE 1

Synthesis of Chlorogallium Phthalocyanine:

30 parts of 1,3-diiminoisoindoline and 9.1 parts of gallium trichloride were put in 230 parts of quinoline and reacted for 3 hours at 200° C. The product formed was taken out by filtration and then washed with acetone and methanol. The wet cake formed was dried to obtain 28 parts of chlorogallium phthalocyanine crystals.

Synthesis of Hydroxygallium phthalocyanine:

3 parts of the chlorogallium phthalocyanine crystals obtained above were dissolved in 60 parts of concentrated sulfuric acid at 0° C., and the resulting solution was dropped into 450 parts of distilled water at 5° C. whereupon crystals precipitated out. After washed with distilled water and dilute aqueous ammonia and dried, 2.5 parts of hydroxygallium phthalocyanine crystals were obtained. FIG. 5 shows the powder X-ray diffraction pattern of the resulting crystals.

The IR spectrum of the thus obtained hydroxygallium phthalocyanine crystals is shown in FIG. 6, and the data (%) of elementary analysis of them are shown in Table 1 below.

                  TABLE 1                                                          ______________________________________                                         Elementary Analysis of Hydroxygallium Phthalocyanine                           (C.sub.32 H.sub.17 N.sub.8 OGa)                                                Elementary                                                                     Analysis     C      H          N    Cl                                         ______________________________________                                         Calculated   64.14  2.86       18.70                                                                               --                                         Measured     62.06  2.67       17.62                                                                               0.46                                       ______________________________________                                    

SYNTHESIS EXAMPLE 2

The hydroxygallium phthalocyanine crystals as obtained in Synthesis Example 1 were ground in an automatic mortar grinder for 55 hours to obtain an amorphous hydroxygallium phthalocyanine. FIG. 7 shows the powder X-ray diffraction pattern of the product.

EXAMPLE 1

0.5 part of the hydroxygallium phthalocyanine crystals as obtained in Synthesis Example 1 were milled along with 15 parts of dimethylformamide and 30 parts of 1 mm-diameter glass beads for 24 hours, and the milled crystals were separated. Next, these were washed with methanol and dried to obtain 0.4 part of hydroxygallium phthalocyanine crystals. FIG. 8 shows the powder X-ray diffraction pattern of the crystals.

The IR spectrum of the thus obtained hydroxygallium phthalocyanine crystals is shown in FIG. 9, the data (%) of elementary analysis of them are shown in Table 2 below, and the visible-infrared absorption spectrum of them is shown in FIG. 20.

                  TABLE 2                                                          ______________________________________                                         Elementary Analysis of Hydroxygallium Phthalocyanine                           (C.sub.32 H.sub.17 N.sub.8 OGa)                                                Elementary                                                                     Analysis     C      H          N    Cl                                         ______________________________________                                         Calculated   64.14  2.86       18.70                                                                               --                                         Measured     63.26  2.77       18.44                                                                               0.33                                       ______________________________________                                    

EXAMPLE 2

The same process as that in Example 1 was repeated, except that the washing solvent was replaced by n-butyl acetate, to obtain 0.4 part of hydroxygallium phthalocyanine crystals. FIG. 10 shows the powder X-ray diffraction pattern of the crystals. The IR spectrum of the crystals was same as that of FIG. 9.

EXAMPLE 3

1.2 parts of the hydroxygallium phthalocyanine crystals as obtained in Synthesis Example 2 were stirred along with 15 parts of n-butyl acetate at 100° C. for 7 hours, and the crystals were then separated. These were washed with n-butyl acetate and dried to obtain 1.0 part of hydroxygallium phthalocyanine crystals. FIG. 11 shows the powder X-ray diffraction pattern of the crystals.

EXAMPLE 4

1.2 parts of the hydroxygallium phthalocyanine crystals as obtained in Synthesis Example 2 were stirred along with 15 parts of methyl ethyl ketone at 60° C. for 7 hours, and the crystals were then separated. These were washed with methyl ethyl ketone and dried to obtain 1.0 part of hydroxygallium phthalocyanine crystals. FIG. 12 shows the powder X-ray diffraction pattern of the crystals.

EXAMPLE 5

The same process as that in Example 1 was repeated, except that the solvent for milling and the washing solvent were replaced by dimethylsulfoxide and n-butyl acetate, respectively, to obtain 0.4 part of hydroxygallium phthalocyanine crystals. FIG. 13 shows the powder X-ray diffraction pattern of the crystals.

EXAMPLE 6

0.5 part of the hydroxygallium phthalocyanine crystals as obtained in Synthesis Example 1 were added to 15 parts of chloroform and stirred at room temperature for 7 hours. The crystals were then separated. These were washed with methanol and dried to obtain 0.4 part of hydroxygallium phthalocyanine crystals. FIG. 14 shows the powder X-ray diffraction pattern of the crystals.

EXAMPLE 7

0.5 part of the hydroxygallium phthalocyanine crystals as obtained in Synthesis Example 2 were milled along with 15 parts of methanol and 30 parts of 1 mm-diameter glass beads for 24 hours. Then, the crystals were separated and dried to obtain 0.4 part of hydroxygallium phthalocyanine crystals. The powder X-ray diffraction pattern of the crystals was same as that of FIG. 14.

EXAMPLE 8

0.5 part of the hydroxygallium phthalocyanine crystals as obtained in Synthesis Example 2 were milled along with 15 parts of dimethylsulfoxide and 30 parts of 1 mm-diameter glass beads for 24 hours. Then, the crystals were separated, washed with methanol and dried to obtain 0.4 part of hydroxygallium phthalocyanine crystals. FIG. 15 shows the powder X-ray diffraction pattern of the crystals.

EXAMPLE 9

The same process as that in Example 8 was repeated, except that the solvent for milling was replaced by piperidine, to obtain 0.4 part of hydroxygallium phthalocyanine crystals. The X-ray powder diffraction pattern of the crystals was same as that of FIG. 15.

EXAMPLE 10

The same process as that in Example 8 was repeated, except that the solvent for milling was replaced by benzyl alcohol, to obtain 0.4 part of hydroxygallium phthalocyanine crystals. FIG. 16 shows the powder X-ray diffraction pattern of the crystals.

EXAMPLE 11

0.5 part of the hydroxygallium phthalocyanine crystals as obtained in Synthesis Example 1 were added to 5 parts of ethylene glycol and stirred at 100° C. for 7 hours. Then, the crystal was separated, washed with methanol and dried to obtain 0.4 part of hydroxygallium phthalocyanine crystals. FIG. 17 shows the powder X-ray diffraction pattern of the crystals.

EXAMPLES 12 TO 20

0.1 part of anyone of the hydroxygallium phthalocyanine crystals each having the X-ray diffraction pattern of one of FIG. 8 and FIGS. 10 to 17, respectively, was mixed with one part of polyvinyl butyral (S-Lec BM-S, trade name by Sekisui Chemical Co.) and 10 parts of cyclohexanone, and the mixture was dispersed by treating it in a paint shaker along with glass beads for one hour. The thus obtained coating composition was coated on an aluminium substrate as the electroconductive support by a dip-coating method and dried under heat at 100° C. for 5 minutes to form thereon a charge generating layer having a thickness of 0.2 μm.

Next, one part of N,N'-diphenyl-N,N'-bis-(m-tolyl)benzidine having the following structural formula (1): ##STR9## and one part of poly[1,1-di-(p-phenylene)cyclohexane carbonate] having the following structural formula (2): ##STR10## were dissolved in 8 parts of chlorobenzene, and the resulting coating composition was coated over the charge generating layer as formed on the aluminium substrate, by a dip-coating method, and dried at 120° C. for one hour to form thereon a charge transporting layer having a thickness of 20 μm.

The electrophotographic photoreceptor thus prepared was examined with respect to the following electrophotographic characteristics, under a normal temperature and normal humidity condition (20° C., 40% RH), a low temperature and low humidity condition (10° C., 15% RH) and a high temperature and high humidity condition (28° C., 80% RH), using an electrostatic duplicating paper test device (Electrostatic Analyzer EPA-8100 Model, manufactured by Kawaguchi Denki Co.).

V_(DPP) : Surface potential in one second after -6.0 KV corona discharge for negative charging.

E_(1/2) : A 800 nm spectral light derived from a band pass filter was irradiated, and the exposure amount of the light necessary for lowering the surface potential to 1/2 of the initial potential was measured to be E_(1/2).

V_(RP) : Surface potential after irradiation of a white light of 50 erg/cm² for 0.5 second.

ΔE*_(1/2) : Amount of environment-dependant fluctuation of E_(1/2) as measured under various ambient conditions.

ΔV_(DDP) : Amount of fluctuation between V_(DDP) after 1,000 times repetition of the above-mentioned charging and exposure and the initial V_(DDP).

ΔE_(1/2) : Amount of fluctuation of E_(1/2) after 1,000 times repetition of the above-mentioned charging and exposure.

ΔV_(RP) : Amount of fluctuation between after V_(RP) after 1,000 times repetition of the above-mentioned charging and exposure and the initial V_(RP).

The results obtained are shown in Table 3 below.

COMPARATIVE EXAMPLE 1

A comparative electrophotographic photoreceptor was prepared in the same manner as in Example 12, except that 0.1 part of the hydroxygallium phthalocyanine crystals obtained in Synthesis Example 1 were used. This was examined to determine the electrophotographic characteristics also in the same manner as above, and the results obtained are shown in Table 3.

                                      TABLE 3                                      __________________________________________________________________________            Charge              environment                                                Generating                                                                            Initial Characteristics                                                                     stability                                                                             Stability and Durability                            Layer  V.sub.DDP                                                                          E.sub.1/2                                                                            VRP                                                                               .increment.E*.sub.1/2                                                                 .increment.V.sub.DDP                                                               .increment.E.sub.1/2                                                                 .increment.VRP                     Example                                                                               Crystals Used                                                                         (V) (erg/cm.sup.2)                                                                       (V)                                                                               (erg/cm.sup.2)                                                                        (V) (erg/cm.sup.2)                                                                       (V)                                __________________________________________________________________________     Example 12                                                                            Example 1                                                                             -800                                                                               2.1   20 0.1    25  0.3   10                                        (FIG. 8)                                                                Example 13                                                                            Example 2                                                                             -800                                                                               2.1   20 0.1    25  0.3    9                                        (FIG. 10)                                                               Example 14                                                                            Example 3                                                                             -790                                                                               2.2   20 0.1    30  0.3   10                                        (FIG. 11)                                                               Example 15                                                                            Example 4                                                                             -780                                                                               2.2   25 0.1    25  0.3    9                                        (FIG. 12)                                                               Example 16                                                                            Example 5                                                                             -770                                                                               2.2   20 0.1    25  0.3   10                                        (FIG. 13)                                                               Example 17                                                                            Example 6                                                                             -830                                                                               2.5   25 0.1    30  0.1   10                                        (FIG. 14)                                                               Example 18                                                                            Example 8                                                                             -790                                                                               2.5   20 0.1    25  0.1    9                                        (FIG. 15)                                                               Example 19                                                                            Example 10                                                                            -750                                                                               3.4   20 0.1    30  0.1   13                                        (FIG. 16)                                                               Example 20                                                                            Example 11                                                                            -830                                                                               2.8   25 0.1    20  0.1   11                                        (FIG. 17)                                                               Comparative                                                                           Synthesis                                                                             -750                                                                               4.2   25 0.2    100 0.2   19                                 Example 1                                                                             Example 1                                                                      (FIG. 5)                                                                __________________________________________________________________________

EXAMPLE 21

A solution composed of one part of an alcohol-soluble nylon resin (Luckamide L-5003, product by Dai-Nippon Ink Chemicals Co.) and 10 parts of methanol was coated on an aluminium substrate by a dip coating method and dried under heat at 120° C. for 10 minutes to form a subbing layer having a thickness of 0.5 μm.

One park of the hydroxygallium phthalocyanine crystals as obtained in Example 1 was mixed with one part of a partially acetacetalized polyvinyl butyral resin (S-Lec BX-L, product by Sekisui Chemical Co.) and 100 parts of n-butyl acetate, and the resulting mixture was treated in a paint shaker along with glass beads to form a resin dispersion. The thus obtained coating composition was coated on the subbing layer by a dip coating method and dried under heat at 100° C. for 10 minutes to form a charge generating layer having a thickness of 0.15 μm. It was confirmed that the crystal form of the hydroxygallium phthalocyanine crystals did not change after dispersion by X-ray diffraction.

2 parts of N,N'-diphenyl-N,N'-bis-(m-tolyl)benzidine of formula (1) and 3 parts of poly[1,1-di-(p-phenylene)cyclohexane carbonate] of formula (2) were dissolved in 20 parts of chlorobenzene, and the coating composition thus obtained was coated over the charge generating layer formed on the aluminium substrate by a dip coating method and dried under heat at 120° C. for one hour to form thereon a charge transporting layer having a thickness of 20 μm.

The electrophotographic photoreceptor thus prepared was examined with respect to the electrophotographic characteristics in the manner mentioned below.

The electrophotographic photoreceptor was subjected to corona discharging of -6 KV so as to be charged under a normal temperature and normal humidity condition (20° C., 40% RH), using an electrostatic duplicating paper test device (Electrostatic Analyzer EPA-8100 Model, manufactured by Kawaguchi Denki Co.). Then an 800-nm monochromatic light as derived from a tungsten lamp with a monochrometer was irradiated to the photoreceptor, the irradiated intensity being adjusted to be 1 μW/cm². The initial surface potential V₀ (volt) and the half-value exposure amount E_(1/2) (erg/cm²) were measured. Next, a white light of 10 luxes was irradiated to the surface of the photoreceptor for one second, and the residual potential V_(R) (volt) was measured. Further, the charging and exposure cycle was repeated 1,000 times whereupon V₀, E_(1/2) and V_(R) were measured.

The hydroxygallium phthalocyanine crystals and the binder resin of constituting the charge generating layer 1 and the measured results as well as the fluctuation of the results of ΔV₀, ΔE_(1/2) and ΔV_(R) are shown in Tables 4 and 5, along with those of the following Examples 22 to 27 and Comparative Examples 2 to 4.

EXAMPLE 22

A photoreceptor was prepared in the same manner as in Example 21 except that one part of a partially formalized polyvinyl butyral resin (S-Lec BX-2, product by Sekisui Chemical Co.) was used in place of the partially acetacetalized polyvinyl butyral resin of constituting the charge generating layer. The photoreceptor was examined in the same manner as in Example 21.

EXAMPLE 23

A photoreceptor was prepared in the same manner as in Example 21 except that one part of a polyester resin (Vylon 200, product by Toyo Spinning Co.) was used in place of the partially acetacetalized polyvinyl butyral resin of constituting the charge generating layer. The photoreceptor was examined in the same manner as in Example 21.

EXAMPLE 24

A photoreceptor was prepared in the same manner as in Example 21 except that one part of a polymethyl methacrylate resin (PMMA) (Elbasite 2021, product by DuPont Co.) was used in place of the partially acetacetalized polyvinyl butyral resin of constituting the charge generating layer 1. The photoreceptor was examined in the same manner as in Example 21.

COMPARATIVE EXAMPLE 2

A photoreceptor was prepared in the same manner as in Example 21 except that the hydroxygallium phthalocyanine crystals as obtained in Synthesis Example 1 were used in place of the hydroxygallium phthalocyanine crystals as obtained in Example 1. The photoreceptor was examined in the same manner as in Example 21.

COMPARATIVE EXAMPLE 3

A photoreceptor was prepared in the same manner as in Example 21 except that the hydroxygallium phthalocyanine crystals as obtained in Synthesis Example 2 were used in place of the hydroxygallium phthalocyanine crystals as obtained in Example 1. The photoreceptor was examined in the same manner as in Example 21.

EXAMPLE 25

A solution composed of 10 parts of a zirconium compound (Orgatics ZC540, product by Matsumoto Pharmaceutical Co.), one part of a silane compound (A1110, product by Nippon Unicar Co.), 40 parts of i-propanol and 20 parts of butanol was coated on an aluminium support by a dip coating method and dried under heat at 160° C. for 10 minutes to form a subbing layer having a thickness of 0.1 μm.

One part of the hydroxygallium phthalocyanine crystals as obtained in Example 1 was mixed with one part of a carboxy-modified vinyl chloride-vinyl acetate copolymer (VMCH, product by Union Carbide Co.) and 100 parts of n-butyl acetate and treated in a paint shaker along with glass beads so that the crystals were dispersed in the copolymer solution. The thus obtained coating composition was coated over the subbing layer by a dip coating method and dried at 100° C. for 10 minutes to form thereon a charge generating layer having a thickness of 0.2 μm. It was confirmed that the crystal form of the hydroxygallium phthalocyanine crystals did not change after dispersion by X-ray diffraction.

A charge transporting layer was formed over the charge generating layer in the same manner as in Example 21 except that 2 parts of N,N'-bis-(p-tolyl)-N,N'-bis-(p-ethylphenyl)-3,3'-dimethylbenzidine having the following structural formula (3) was used in place of N,N'-diphenyl-N,N-bis-(m-tolyl)-benzidine of formula (2). The photoreceptor sample prepared was then examined in the same manner as in Example 21. ##STR11##

EXAMPLE 26

A photoreceptor was prepared in the same manner as in Example 25 except that one part of a phenoxy resin (PKHH, product by Union Carbide Co.) and 100 parts of cyclohexanone were used in place of the modified vinyl chloride-vinyl acetate copolymer of constituting the charge generating layer 1. The photoreceptor was examined in the same manner as in Example 21.

EXAMPLE 27

A photoreceptor was prepared in the same manner as in Example 25 except that one part of a modified ether type polyester resin (STAFIX NLC-2, product by Fuji Photo Film Co.) and 100 parts of cyclohexanone were used in place of the modified vinyl chloride-vinyl acetate copolymer of constituting the charge generating layer 1. The photoreceptor was examined in the same manner as in Example 21.

COMPARATIVE EXAMPLE 4

A photoreceptor was prepared in the same manner as in Example 25 except that the hydroxygallium phthalocyanine crystals as obtained in Synthesis Example 1 were used in place of the hydroxygallium phthalocyanine crystals as obtained in Example 1. The photoreceptor was examined in the same manner as in Example 21.

                  TABLE 4                                                          ______________________________________                                                Charge Generating Layer                                                          Crystals Used (X-                                                              ray Diffraction                                                       Example No.                                                                             Pattern)     Binder Resin Used                                        ______________________________________                                         Example 21                                                                              FIG. 8       partially acetacetalized                                                       polyvinyl butyral                                        Example 22                                                                              FIG. 8       partially formalized polyvinyl                                                 butyral                                                  Example 23                                                                              FIG. 8       polyester                                                Example 24                                                                              FIG. 8       PMMA                                                     Example 25                                                                              FIG. 8       carboxy-modified vinyl chlo-                                                   ride-vinyl acetate copolymer                             Example 26                                                                              FIG. 8       phenoxy resin                                            Example 27                                                                              FIG. 8       modified ether type polyester                            Comparative                                                                             FIG. 5       partially acetacetalized poly-                           Example 2             vinyl butyral                                            Comparative                                                                             FIG. 7       partially acetacetalized poly-                           Example 3             vinyl butyral                                            Comparative                                                                             FIG. 5       carboxy-modified vinyl chlo-                             Example 4             ride-vinyl acetate copolymer                             ______________________________________                                    

                                      TABLE 5                                      __________________________________________________________________________                         Retained Characteristics                                          Initial Characteristics                                                                     (after 1,000 repetitions)                                                                   Stability                                                                            Durability                                     V.sub.0                                                                            E.sub.1/2                                                                            V.sub.RP                                                                          V.sub.0                                                                            E.sub.1/2                                                                            V.sub.RP                                                                          .increment.E*.sub.1/2                                                                .increment.V.sub.0                                                                .increment.V.sub.RP                  Example No.                                                                           (V) (erg/cm.sup.2)                                                                       (V)                                                                               (V) (erg/cm.sup.2)                                                                       (V)                                                                               (erg/cm.sup.2)                                                                       (V)                                                                               (V)                                  __________________________________________________________________________     Example 21                                                                            -815                                                                               2.2   -21                                                                               -803                                                                               2.5   -26                                                                               0.3   12  5                                   Example 22                                                                            -821                                                                               2.3   -18                                                                               -813                                                                               2.5   -24                                                                               0.2    8  6                                   Example 23                                                                            -720                                                                               3.0   -39                                                                               -656                                                                               3.9   -52                                                                               0.9   64 13                                   Example 24                                                                            -729                                                                               3.4   -48                                                                               -668                                                                               4.2   -63                                                                               0.8   61 15                                   Example 25                                                                            -803                                                                               1.9   -15                                                                               -789                                                                               2.2   -22                                                                               0.3   14  7                                   Example 26                                                                            -815                                                                               2.1   -26                                                                               -803                                                                               2.3   -30                                                                               0.2   12  4                                   Example 27                                                                            -821                                                                               1.9   -21                                                                               -811                                                                               2.0   -25                                                                               0.1   10  4                                   Comparative                                                                           -742                                                                               4.3   - 32                                                                              -637                                                                               5.1   -49                                                                               0.8   69 17                                   Example 2                                                                      Comparative                                                                           -723                                                                               5.2   -47                                                                               -655                                                                               6.3   -63                                                                               1.1   68 16                                   Example 3                                                                      Comparative                                                                           -724                                                                               3.7   -28                                                                               -651                                                                               4.9   -42                                                                               1.2   73 14                                   Example 4                                                                      __________________________________________________________________________

EXAMPLES 28 TO 32

Drum type electrophotographic photoreceptors were prepared under the same conditions as those in Examples 21, 22 and 25 to 27. Each of them was set in a semiconductor laser printer (FX XP-15 Model, manufactured by Fuji Xerox Co.) and duplicated images were formed. Duplication was repeated 10,000 times and measured for the property of the CGL coat layer and formation of the image deffects. The results are shown in Table 6 below.

                  TABLE 6                                                          ______________________________________                                                   Property of                                                                            Image Defects                                                            CGL Coat  One         10,000                                       Example No. Layer     Duplication Duplications                                 ______________________________________                                         Example 28  Good      No          No                                           Example 29  Good      No          No                                           Example 30  Good      No          No                                           Example 31  Good      No          No                                           Example 32  Good      No          No                                           ______________________________________                                    

EXAMPLE 33

One part of the hydroxygallium phthalocyanine crystals as obtained in Synthesis Example 1, having the powder X-ray diffraction pattern of FIG. 5, were milled in an attritor along with 18 parts of dimethylformamide and 200 parts of 1/8 inch-diameter steel shots for 16 hours. The thus milled crystals were separated, washed with n-butyl acetate and dried to obtain 0.9 part of hydroxygallium phthalocyanine crystals. FIG. 18 shows the powder X-ray diffraction pattern of the crystals. FIG. 19 shows the visible infrared absorption spectrum of the crystals.

It can be understood from FIG. 18 that the resulting crystals had distinct diffraction peaks at 7.4°, 9.9°, 25.0°, 26.0° and 28.2° of the Bragg angle (2θ±0.2) in the X-ray diffraction spectrum.

An electrophotographic photoreceptor was prepared in the same manner as in Example 12, except that the above-obtained hydroxygallium phthalocyanine crystals were used. This was examined to determine the electrophotographic characteristics the same manner as in Example 12. The results obtained are as follows:

V_(DDP) : -810 (V)

E_(1/2) : 2.1 (erg/cm²)

V_(RP) : 25 (V)

E*_(1/2) : 0.1 (erg/cm²)

ΔV_(DDP) : 25 (V)

ΔE_(1/2) : 0.3 (erg/cm²)

ΔV_(RP) : 10 (V)

EXAMPLE 34

A solution composed of 10 parts of a zirconium compound ("Orgatics ZC 540" produced by Matsumoto Pharmaceutical Co.), 1 part of a silane compound ("A1110" produced by Nippon Unicar Co.), 40 parts of isopropyl alcohol, and 20 parts of butyl alcohol was coated on an aluminum support by dip coating and dried under heat at 150° C. for 10 minutes to form a subbing layer having a thickness of 0.5 μm.

One part of the hydroxygallium phthalocyanine crystals as obtained in Example 1 was mixed with 1 part of a polyvinyl butyral resin ("S-Lec BM-S" produced by Sekisui Chemical Co.) and 100 parts of n-butyl acetate, and the resulting mixture was treated in a .paint shaker together with glass beads for 1 hour to form a coating composition. The coating composition was coated on the subbing layer by dip coating and dried by heating at 100° C. for 10 minutes to form a charge generating layer having a thickness of 0.15 μm. X-Ray diffractometry of the dispersed hydroxygallium phthalocyanine crystals revealed that the crystal form had not changed on being dispersed.

In 20 parts of monochlorobenzene were dissolved 2 parts of a compound of formula (II) wherein R₅ is H, R₆ is 3-CH₃, and R₇ is H and 3 parts of poly(4,4'-cyclohexylidenediphenylene carbonate) represented by formula (XIII): ##STR12##

Mw=39000 (viscosity-average molecular weight) and the resulting coating composition was coated on the charge generating layer by dip coating and dried by heating at 120° C. for 1 hour to form a charge transporting layer having a thickness of 20 μm.

Electrophotographic characteristics of the thus prepared electrophotographic photoreceptor were evaluated by using an electrostatic analyzer "EPA-8100" manufactured by Kawaguchi Denki Co. The photoreceptor was charged to -6 kV by a corona discharge under a normal temperature and normal humidity condition (20° C., 40% RH) and then exposed to monochromatic light of 800 nm, which was isolated from light emitted from a tungsten lamp by means of a monochromator and adjusted to 1 μW/cm² on the surface of the photoreceptor. The surface potential V₀ (V) and the exposure amount necessary for reducing the surface potential to 1/2 of the initial potential E_(1/2) (erg/cm²) were measured. Then, the photoreceptor was exposed to white light of 10 lux for 1 second, and the residual potential V_(RP) (V) was measured. The above charging and exposure were repeated 1000 times, and V₀, E_(1/2), and V_(RP) were measured. The changes in V₀, E_(1/2), and V_(RP) after the repetition were expressed as ΔV₀, ΔE_(1/2), and ΔV_(RP), respectively. The results of these measurements are shown in Table 9 below.

EXAMPLES 35 TO 43

A photoreceptor was prepared and evaluated in the same manner as in Example 1, except for replacing the charge transporting material used in Example 34 with each of the materials shown in Table 7 below. The results of evaluation are shown in Table 9.

EXAMPLE 44

A solution comprising 10 parts of a zirconium compound ("Orgatics ZC 540" produced by Matsumoto Pharmaceutical Co.), 1 part of a silane compound ("A1110" produced by Nippon Unicar Co.), 40 parts of isopropyl alcohol, and 20 parts of butyl alcohol was coated on an aluminum support by dip coating and dried under heat at 150° C. for 10 minutes to form a subbing layer having a thickness of 0.5 μm. One part of the hydroxygallium phthalocyanine crystals as obtained in Example 1 was mixed with 1 part of a polyvinyl butyral resin ("S-Lec BM-S" produced by Sekisui Chemical Co.) and 100 parts of n-butyl acetate, and the resulting mixture was treated in a paint shaker together with glass beads for 1 hour to form a coating composition. The coating composition was coated on the subbing layer by dip coating and dried by heating at 100° C. for 10 minutes to form a charge generating layer having a thickness of 0.15 μm. X-kay diffractometry of the dispersed hydroxygallium phthalocyanine crystals revealed that the crystal form had not changed on being dispersed.

In 20 parts of monochlorobenzene were dissolved 2 parts of a compound of formula (III) wherein R₈, R₉ and R₁₀ are hydrogen atoms and 3 parts of the polycarbonate of formula (XIII), and the resulting coating composition was coated on the charge generating layer by dip coating and dried by heating at 120° C. for 1 hour to form a charge transporting layer having a thickness of 20 μm.

Electrophotographic characteristics of the electrophotographic photoreceptors prepared above were evaluated by using an electrostatic analyzer "EPA-8100" manufactured by Kawaguchi Denki Co. Each photoreceptor was charged to -6 kV by a corona discharge under a normal temperature and normal humidity condition (20° C., 40% RH) and then exposed to monochromatic light of 800 nm, isolated from light emitted from a tungsten lamp by means of a monochromator and adjusted to 1 μW/cm² on the surface of the photoreceptor. The surface potential V₀ (V) and the exposure amount necessary for reducing the surface potential to 1/2 of the initial potential E_(1/2) (erg/cm²) were measured. Then, the photoreceptor was exposed to white light of 10 lux for 1 second, and the residual potential V_(RP) (V) was measured. The above charging and exposure were repeated 1000 times, and V₀, E_(1/2), and V_(RP) were measured. The changes in V₀, E_(1/2), and V_(RP) after the repetition were expressed as ΔV₀, ΔE_(1/2), and ΔV_(RP), respectively. The results of these measurements are shown in Table 9 below.

EXAMPLES 45 TO 47

A photoreceptor was prepared and evaluated in the same manner as in Example 44, except for replacing the charge transporting material as used in Example 44 with each of the materials shown in Table 8. The results of evaluation are shown in Table 9 below.

                  TABLE 7                                                          ______________________________________                                                      Charge                                                            Example      Transporting material (II)                                        No.          R.sub.5   (R.sub.6).sub.p                                                                           (R.sub.7).sub.q                              ______________________________________                                         Example 34   H         3-CH.sub.3 H                                            Example 35   CH.sub.3  4-CH.sub.3 4'-CH.sub.3                                  Example 36   CH.sub.3  3,4-CH.sub.3                                                                              3',4'-CH.sub.3                               Example 37   CH.sub.3  4-C.sub.2 H.sub.5                                                                         4'-CH.sub.3                                  Example 38   CH.sub.3  4-C.sub.4 H.sub.9                                                                         4'-CH.sub.3                                  Example 39   CH.sub.3  4-C.sub.2 H.sub.5                                                                         4'-OCH.sub.3                                 Example 40   Cl        3-CH.sub.3 H                                            Example 41   C.sub.2 H.sub.5                                                                          4-CH.sub.3 4'-CH.sub.3                                  Example 42   OCH.sub.3 2-CH.sub.3 H                                            Example 43   C.sub.2 H.sub.5                                                                          4-C.sub.3 H.sub.7                                                                         4'-CH.sub.3                                  ______________________________________                                    

                  TABLE 8                                                          ______________________________________                                                     Charge                                                             Example     Transporting material (II)                                         No.         R.sub.8    R.sub.9      R.sub.10                                   ______________________________________                                         Example 44  H          H            H                                          Example 45  3-CH.sub.3 3-CH.sub.3   H                                          Example 46  4-CH.sub.3 4-CH.sub.3   H                                          Example 47  3-OCH.sub.3                                                                               3-OCH.sub.3  H                                          ______________________________________                                    

                                      TABLE 9                                      __________________________________________________________________________                        Retained Characteristics                                    Initial Characteristics                                                                           (after 1,000 Repetitions)                                                                   Stability                                                                            Durability                               Example                                                                              V.sub.0                                                                            E.sub.1/2                                                                            V.sub.RP                                                                          V.sub.0                                                                            E.sub.1/2                                                                            V.sub.RP                                                                          .sup..increment. E.sub.1/2                                                           .sup..increment. V.sub.0                                                          .sup..increment. V.sub.RP             No.   (V) (erg/cm.sup.2)                                                                       (V)                                                                               (V) (erg/cm.sup.2)                                                                       (V)                                                                               (erg/cm.sup.2)                                                                       (V)                                                                               (V)                                   __________________________________________________________________________     Example 34                                                                           -815                                                                               2.2   -21                                                                               -803                                                                               2.5   -26                                                                               0.3   12 5                                     Example 35                                                                           -807                                                                               2.1   -23                                                                               -796                                                                               2.4   -25                                                                               0.3   11 2                                     Example 36                                                                           -810                                                                               2.3   -24                                                                               -802                                                                               2.5   -30                                                                               0.2    8 6                                     Example 37                                                                           -802                                                                               2.0   -25                                                                               -795                                                                               2.2   -28                                                                               0.2    7 3                                     Example 38                                                                           -810                                                                               2.3   -24                                                                               -798                                                                               2.7   -27                                                                               0.4   12 3                                     Example 39                                                                           -804                                                                               2.0   -24                                                                               -795                                                                               2.3   -24                                                                               0.3    9 0                                     Example 40                                                                           -813                                                                               2.4   -21                                                                               -799                                                                               2.6   -23                                                                               0.2   14 2                                     Example 41                                                                           -805                                                                               2.2   -25                                                                               -792                                                                               2.6   -25                                                                               0.4   13 0                                     Example 42                                                                           -801                                                                               2.1   -24                                                                               -789                                                                               2.3   -23                                                                               0.2   12 1                                     Example 43                                                                           -815                                                                               2.5   -27                                                                               -803                                                                               2.8   -31                                                                               0.3   12 4                                     Example 44                                                                           -820                                                                               2.5   -39                                                                               -805                                                                               2.9   -50                                                                               0.4   15 11                                    Example 45                                                                           -806                                                                               2.4   -35                                                                               -792                                                                               2.8   -46                                                                               0.4   14 11                                    Example 46                                                                           -801                                                                               2.4   -31                                                                               -785                                                                               2.9   -47                                                                               0.5   16 10                                    Example 47                                                                           -794                                                                               2.4   -28                                                                               -774                                                                               2.9   -43                                                                               0.5   20 15                                    __________________________________________________________________________

EXAMPLE 48

An electrophotographic photoreceptor was prepared and evaluated in the same manner as in Example 34, except for using the following composition as a subbing layer and changing the subbing layer thickness to 0.9 μm. The results of evaluation are shown in Table 10 below.

    ______________________________________                                         Subbing Layer Composition:                                                     ______________________________________                                         Butoxyacetylacetonatozirconium                                                                           20    parts                                          ("Orgatics ZC 540" produced by                                                 Matsumoto Pharmaceutical Co.)                                                  γ-Aminopropyltriethoxysilane                                                                       2     parts                                          ("A1100" produced by Nippon Unicar Co.)                                        Polyvinyl butyral resin ("S-Lec BM-S"                                                                    1.5   parts                                          produced by Sekisui Chemical Co.)                                              n-Butyl alcohol           70    parts                                          ______________________________________                                    

EXAMPLE 49

An electrophotographic photoreceptor was prepared and evaluated in the same manner as in Example 34, except for using the following composition as a subbing layer and changing the subbing layer thickness to 0.5 μm. The results of evaluation are shown in Table 10.

    ______________________________________                                         Subbing Layer Composition:                                                     ______________________________________                                         Zirconium n-butoxide ("Orgatics ZA 60"                                                                    20    parts                                         produced by Matsumoto Pharmaceutical Co.)                                      γ-Aminopropyltriethoxysilane                                                                        2     parts                                         ("A1100" produced by Nippon Unicar Co.)                                        Polyvinyl butyral resin ("S-Lec BM-S"                                                                     1.5   parts                                         produced by Sekisui Chemical Co.)                                              n-Butyl alcohol            70    parts                                         ______________________________________                                    

EXAMPLE 50

An electrophotographic photoreceptor was prepared and evaluated in the same manner as in Example 34, except for using the same subbing layer composition as used in Example 48 with its polyvinyl butyral resin being replaced by a polyvinyl formal resin ("Denka Formal #20). The results of evaluation are shown in Table 10.

EXAMPLE 51

An electrophotographic photoreceptor was prepared and evaluated in the same manner as in Example 34, except for using the following composition as a subbing layer and changing the subbing layer thickness to 0.9 μm. The results of evaluation are shown in Table 10.

    ______________________________________                                         Subbing Layer Composition:                                                     ______________________________________                                         Acetylacetonatotitanium ("Orgatics TC 100"                                                                10    parts                                         produced by Matsumoto Pharmaceutical Co.)                                      γ-(2-Aminoethyl)aminopropyltrimethoxy-                                                              1     part                                          silane                                                                         Polyvinyl butyral resin ("S-Lec BM-1"                                                                     1.5   parts                                         produced by Sekisui Chemical Co.)                                              Isopropyl alcohol          70    parts                                         ______________________________________                                    

EXAMPLE 52

An electrophotographic photoreceptor was prepared and evaluated in the same manner as in Example 34, except for using the following composition as a subbing layer and changing the subbing layer thickness to 0.9 μm. The results of evaluation are shown in Table 10.

    ______________________________________                                         Subbing Layer Composition:                                                     ______________________________________                                         Acetylacetonatotin        5     parts                                          γ-(2-Aminoethyl)aminopropyltri-                                                                    1     part                                           methoxysilane                                                                  Polyvinyl butyral resin ("S-Lec BM-S"                                                                    1.5   parts                                          produced by Sekisui Chemical Co.)                                              n-Butyl alcohol           70    parts                                          ______________________________________                                    

EXAMPLE 53

An electrophotographic photoreceptor was prepared and evaluated in the same manner as in Example 34, except for using the following composition as a subbing layer and changing the subbing layer thickness to 0.9 μm. The results of evaluation are shown in Table 10.

    ______________________________________                                         Subbing Layer Composition:                                                     ______________________________________                                         Trisacetylacetonatoaluminum                                                                              5     parts                                          ("Alumi Chelate A" produced by                                                 Kawaken Fine Chemical Co., Ltd.)                                               γ-Aminopropyltriethoxysilane                                                                       1     part                                           Polyvinyl butyral resin ("S-Lec BM-S"                                                                    1.5   parts                                          produced by Sekisui Chemical Co.)                                              n-Butyl alcohol           80    parts                                          ______________________________________                                    

                                      TABLE 10                                     __________________________________________________________________________                        Retained Characteristics                                    Initial Characteristics                                                                           (after 1,000 Repetitions)                                                                   Stability                                                                            Durability                               Example                                                                              V.sub.0                                                                            E.sub.1/2                                                                            V.sub.RP                                                                          V.sub.0                                                                            E.sub.1/2                                                                            V.sub.RP                                                                          .sup..increment. E.sub.1/2                                                           .sup..increment. V.sub.0                                                          .sup..increment. V.sub.RP             No.   (V) (erg/cm.sup.2)                                                                       (V)                                                                               (V) (erg/cm.sup.2)                                                                       (V)                                                                               (erg/cm.sup.2)                                                                       (V)                                                                               (V)                                   __________________________________________________________________________     Example 48                                                                           -820                                                                               2.3   -26                                                                               -810                                                                               2.6   -32                                                                               0.4   10 6                                     Example 49                                                                           -818                                                                               2.2   -25                                                                               -809                                                                               2.5   -30                                                                               0.3    9 5                                     Example 50                                                                           -815                                                                               2.3   -24                                                                               -804                                                                               2.7   -29                                                                               0.4   11 4                                     Example 51                                                                           -820                                                                               2.4   -27                                                                               -805                                                                               2.7   -31                                                                               0.3   15 4                                     Example 52                                                                           -819                                                                               2.5   -27                                                                               -810                                                                               2.8   -33                                                                               0.3    9 6                                     Example 53                                                                           -814                                                                               2.4   -25                                                                               -801                                                                               2.7   -29                                                                               0.3   13 4                                     __________________________________________________________________________

EXAMPLE 54

A solution comprising 10 parts of a zirconium compound ("Orgatics ZC 540" produced by Matsumoto Pharmaceutical Co.), 1 part of a silane compound ("A1110" produced by Nippon Unicar Co.), 40 parts of isopropyl alcohol, and 20 parts of n-butyl alcohol was coated on an aluminum support by dip coating and dried under heat at 150° C. for 10 minutes to form a subbing layer having a thickness of 0.5 μm. One part of the hydroxygallium phthalocyanine crystals as obtained in Example 1 was mixed with 1 part of a polyvinyl butyral resin ("S-Lec BM-S" produced by Sekisui Chemical Co.) and 100 parts of n-butyl acetate, and the resulting mixture was dispersed in a paint shaker together with glass beads for 1 hour to form a coating composition. The coating composition was coated on the subbing layer by dip coating and dried by heating at 100° C. for 10 minutes to form a charge generating layer having a thickness of 0.15 μm. X-Ray diffractometry of the dispersed hydroxygallium phthalocyanine crystals revealed that the crystal form had not changed on being dispersed.

In 29 parts of monochlorobenzene were dissolved 2 parts of compound (a) shown below and 3 parts of a polycarbonate resin comprising the monomer unit of formula (XIII), and the resulting coating composition was coated on the charge generating layer by dip coating and dried by heating at 120° C. for 1 hour to form a charge transporting layer having a thickness of 20 μm.

Electrophotographic characteristics of the thus prepared electrophotographic photoreceptor was evaluated by using an electrostatic analyzer "EPA-8100" manufactured by Kawaguchi Denki Co. The photoreceptor was charged to -6 kV by a corona discharge under a normal temperature and normal humidity condition (20° C. 40% RH) and then exposed to monochromatic light of 800 nm, isolated from light emitted from a tungsten lamp by means of a monochromator and adjusted to 1 μW/cm² on the surface of the photoreceptor. The surface potential V₀ (V) and the exposure amount necessary for reducing the surface potential to 1/2 of the initial potential E_(1/2) (erg/cm²) were measured. Then, the photoreceptor was exposed to white light of 10 lux for 1 second, and the residual potential V_(RP) (V) was measured. The above charging and exposure were repeated 1000 times, and V₀, E_(1/2), and V_(RP) were measured. The changes in V₀, E_(1/2), and V_(RP) after the repetition were expressed as ΔV₀, ΔE_(1/2), and ΔV_(RP), respectively. The results of these measurements are shown in Table 11 below.

EXAMPLES 55 TO 74

A photoreceptor was prepared and evaluated in the same manner as in Example 54, except for replacing the charge transporting material as used in Example 54 (compound (a)) with each of the compounds shown in Tables 11 and 12 below. The results of evaluation are shown in Tables 11 and 12.

    ______________________________________                                         Compounds (a) to (i):                                                           ##STR13##                                                                     Compound No.                                                                             Y                R.sub.23 R.sub.24                                   ______________________________________                                         (a)       (CH.sub.2).sub.2 H        4-CH.sub.3                                 (b)       (CH.sub.2).sub.3 H        4-CH.sub.3                                 (c)       (CH.sub.2).sub.5 H        4-CH.sub.3                                 (d)       CHCH             H        4-CH.sub.3                                 (e)       COCHCH           H        3-CH.sub.3                                 (f)       CH.sub.2CHCH     H        H                                          (g)       CO(CH.sub.2).sub.3CO                                                                            H        4-CH.sub.3                                 (h)                                                                                       ##STR14##       H        H                                          (i)                                                                                       ##STR15##       4-CH.sub.3                                                                              4-CH.sub.3                                 ______________________________________                                    

    ______________________________________                                         Compounds (j) to (m):                                                           ##STR16##                                                                     Com-                                                                           pound                                                                          No.   R.sub.25                                                                               R.sub.26                                                                               R.sub.27                                                 ______________________________________                                         (j)   H       H       H                                                        (k)   2-CH.sub.3                                                                             4-CH.sub.3                                                                             4-CH.sub.3                                               (l)   4-CH.sub.3                                                                             4-CH.sub.3                                                                             4-CH.sub.3                                               (m)   4-CH.sub.3                                                                             4-CH.sub.3                                                                              ##STR17##                                               ______________________________________                                    

    ______________________________________                                         Compounds (n) to (r):                                                           ##STR18##                                                                     Com-                                                                           pound                                                                          No.   R.sub.28                                                                               R.sub.29 R.sub.30 R.sub.31                                       ______________________________________                                         (n)   H       H                                                                                        ##STR19##                                                                               ##STR20##                                     (o)   H       4-CH.sub.3                                                                              H                                                                                        ##STR21##                                     (p)   H       4-OCH.sub.3                                                                             H                                                                                        ##STR22##                                     (q)   4-CH.sub.3                                                                             4-CH.sub.3                                                                               ##STR23##                                                                               ##STR24##                                     (r)   4-CH.sub.3                                                                             4-CH.sub.3                                                                               ##STR25##                                              ______________________________________                                    

    ______________________________________                                         Compounds (s) to (u):                                                           ##STR26##                                                                     Com-                                                                           pound                                                                          No.   u     R.sub.32  R.sub.33                                                                               R.sub.34                                                                               R.sub.35                                 ______________________________________                                         (s)   0     H         H       4-N(C.sub.2 H.sub.5).sub.2                                                             4-N(C.sub.2 H.sub.5).sub.2               (t)   1     H         H       4-N(C.sub.2 H.sub.5).sub.2                                                             4-N(C.sub.2 H.sub.5).sub.2               (u)   1     4-N(C.sub.2 H.sub.5).sub.2                                                               4-N(C.sub.2 H.sub.5).sub.2                                                             4-N(C.sub.2 H.sub.5).sub.2                                                             4-N(C.sub.2 H.sub.5).sub.2               ______________________________________                                    

                                      TABLE 11                                     __________________________________________________________________________     Charge                 Retained Characteristics                                Trans-    Initial Characteristics                                                                     (after 1000 repetitions)                                                                    Stability                                                                            Durability                           Example                                                                             porting                                                                             V.sub.0                                                                            E.sub.1/2                                                                            V.sub.RP                                                                          V.sub.0                                                                            E.sub.1/2                                                                            V.sub.RP                                                                          .sup..increment. E.sub.1/2                                                           .sup..increment. V.sub.0                                                          .sup..increment. V.sub.RP         No.  Material                                                                            (V) (erg/cm.sup.2)                                                                       (V)                                                                               (V) (erg/cm.sup.2)                                                                       (V)                                                                               (erg/cm.sup.2)                                                                       (V)                                                                               (V)                               __________________________________________________________________________     54   (a)  -825                                                                               2.6   -38                                                                               -811                                                                               3.0   -49                                                                               0.4   14 11                                55   (b)  -824                                                                               2.6   -40                                                                               -809                                                                               3.0   -52                                                                               0.4   15 12                                56   (c)  -825                                                                               2.7   -44                                                                               -810                                                                               3.2   -56                                                                               0.5   15 12                                57   (d)  -813                                                                               2.5   -41                                                                               -799                                                                               2.9   -51                                                                               0.4   14 10                                58   (e)  -836                                                                               2.7   -47                                                                               -824                                                                               3.2   -58                                                                               0.5   12 11                                59   (f)  -811                                                                               2.6   -39                                                                               -798                                                                               3.0   -49                                                                               0.4   13 10                                60   (g)  -839                                                                               2.7   -43                                                                               -824                                                                               3.2   -60                                                                               0.5   15 12                                61   (h)  -819                                                                               2.5   -43                                                                               -807                                                                               2.9   -54                                                                               0.4   12 11                                __________________________________________________________________________

                                      TABLE 12                                     __________________________________________________________________________     Charge                 Retained Characteristics                                Trans-    Initial Characteristics                                                                     (after 1000 repetitions)                                                                    Stability                                                                            Durability                           Example                                                                             porting                                                                             V.sub.0                                                                            E.sub.1/2                                                                            V.sub.RP                                                                          V.sub.0                                                                            E.sub.1/2                                                                            V.sub.RP                                                                          .sup..increment. E.sub.1/2                                                           .sup..increment. V.sub.0                                                          .sup..increment. V.sub.RP         No.  Material                                                                            (V) (erg/cm.sup.2)                                                                       (V)                                                                               (V) (erg/cm.sup.2)                                                                       (V)                                                                               (erg/cm.sup.2)                                                                       (V)                                                                               (V)                               __________________________________________________________________________     62   (i)  -807                                                                               2.4   -34                                                                               -794                                                                               2.7   -46                                                                               0.3   13 12                                63   (j)  -835                                                                               2.8   -40                                                                               -816                                                                               3.4   -55                                                                               0.6   19 15                                64   (k)  -823                                                                               2.6   -37                                                                               -808                                                                               3.1   -51                                                                               0.5   15 14                                65   (l)  -815                                                                               2.5   -31                                                                               -801                                                                               2.9   -43                                                                               0.4   14 12                                66   (m)  -816                                                                               2.5   -33                                                                               -806                                                                               2.9   -48                                                                               0.4   10 15                                67   (n)  -820                                                                               2.5   -37                                                                               -805                                                                               2.9   -47                                                                               0.4   15 10                                68   (o)  -806                                                                               2.6   -31                                                                               -790                                                                               3.1   -45                                                                               0.5   16 14                                69   (p)  -799                                                                               2.6   -29                                                                               -779                                                                               3.1   -40                                                                               0.5   20 11                                70   (q)  -816                                                                               2.5   -35                                                                               -801                                                                               2.9   -45                                                                               0.4   15 10                                71   (r)  -818                                                                               2.5   -32                                                                               -807                                                                               3.0   -44                                                                               0.5   11 12                                72   (s)  -803                                                                               2.8   -40                                                                               -784                                                                               3.3   -55                                                                               0.5   19 15                                73   (t)  -805                                                                               2.8   -38                                                                               -791                                                                               3.2   -52                                                                               0.4   14 14                                74   (u)  -786                                                                               2.8   -31                                                                               -767                                                                               3.3   -46                                                                               0.5   19 15                                __________________________________________________________________________

As has been explained in detail in the above, the chlorogallium phthalocyanine crystals of the present invention have novel crystal forms and the wavelength range of the light to which they are sensitive is extended to a long wavelength range. Therefore, they are extremely useful as photoconductive materials for electrophotographic photoreceptors such as printers of using semiconductor lasers. The electrophotographic photoreceptors of the present invention having the above-mentioned chlorogallium phthalocyanine crystals with a novel crystal form have high sensitivity and are usable as high-durability photoreceptors, since the residual charge is low, the charging property is high and the fluctuation of the characteristics due to repeated use is small.

In particular, electrophotographic photoreceptors each having a light-sensitive layer comprising hydroxygallium phthalocyanine crystals as a charge generating material and a binder resin selected from polyvinyl acetal resins, vinyl chloride-vinyl acetate copolymers, phenoxy resins and modified ether type polyester resins have high sensitivity and good charge retentiveness and coatability. They may form images having few image defects and having extremely excellent image characteristics.

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof. 

What is claimed is:
 1. An electrophotographic photoreceptor comprising a conductive support having thereon a light-sensitive layer containing hydroxygallium phthalocyanine crystals as a charge generating material and a benzidine compound represented by formula (II): ##STR27## wherein R₅ represents a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom; R₆ and R₇ each represent a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, or a substituted amino group; and p and q each represent 0, 1 or 2, or a tetraaryl-m-phenylenediamine compound represented by formula (III): ##STR28## wherein R₈, R₉, and R₁₀ each represent a hydrogen atom, an alkyl group, an alkoxy group, a substituted or unsubstituted aryl group or an aralkyl group, as a charge transporting material.
 2. An electrophotographic photoreceptor as claimed in claim 1, wherein said light-sensitive layer comprises a charge generating layer and a charge transporting layer, said charge generating layer containing said hydroxygallium phthalocyanine crystals, and said charge transporting layer comprising a binder resin containing said benzidine compound represented by formula (II) or said tetraaryl-m-phenylenediamine compound represented by formula (III).
 3. An electrophotographic photoreceptor as claimed in claim 1, wherein said benzidine compound represented by formula (II) is a compound represented by formula (IV): ##STR29## wherein R₁₁ and R₁₂ each represent a hydrogen atom or a methyl group.
 4. An electrophotographic photoreceptor as claimed in claim 1, wherein said benzidine compound represented by formula (II) is a compound represented by formula (V): ##STR30## wherein either one of R₁₃ and R₁₄ represents an alkyl group having 2 or more carbon atoms, with the other representing a hydrogen atom, an alkyl group, an alkoxy group or a substituted amino group.
 5. An electrophotographic photoreceptor as claimed in claim 1, wherein said light-sensitive layer contains more than one kind of hydroxygallium phthalocyanine crystals.
 6. An electrophotographic photoreceptor comprising a conductive support having consecutively thereon at least a subbing layer, a charge generating layer, and a charge transporting layer, wherein said charge generating layer containing hydroxygallium phthalocyanine crystals as a charge generating material and said subbing layer containing an organometallic compound and a silane coupling agent as main components.
 7. An electrophotographic photoreceptor as claimed in claim 1, wherein said subbing layer contains a binder resin compatible with said organometallic compound and said silane coupling agent in an amount of not more than 25% by weight based on the total weight of said organometallic compound and said silane coupling agent.
 8. An electrophotographic photoreceptor as claimed in claim 1, wherein said organometallic compound is an organozirconium compound.
 9. An electrophotographic photoreceptor as claimed in claim 1, wherein said organometallic compound is an organotitanium compound.
 10. An electrophotographic photoreceptor comprising a conductive support having thereon a light-sensitive layer, said light-sensitive layer containing hydroxygallium phthalocyanine crystals as a charge generating material and a compound represented by formula (XVII), (XVIII), (XIX) or (XX) as a charge transporting material: ##STR31## wherein R₂₃ and R₂₄ each represent a hydrogen atom, an alkyl group or an aryl group; Y represents --(C(CH₃)₂)--, --(CH₂)_(t) --, wherein t represents an integer of from 1 to 5, --(OCH₂ CH₂)_(t) --, wherein t represents an integer of from 1 to 5, --CH═CH--, --CO(CH₂)₂ --, --CO(CH₂)₃ --, a cyclobenzylidene group or a cyclohexylidene group; ##STR32## wherein R₂₅, R₂₆, and R₂₇ each represent a hydrogen atom, an alkyl group, a substituted or unsubstituted aryl group or an aralkyl group; ##STR33## wherein R₂₈ and R₂₉ each represent a hydrogen atom, a halogen atom, an alkyl group or a substituted or unsubstituted aryl group; and R₃₀ and R₃₁ each represent a hydrogen atom, an alkyl group or a substituted or unsubstituted aryl group, or R₃₀ and R₃₁ are taken together to form an atomic group forming a condensed carbon ring;. ##STR34## wherein R₃₂, R₃₃, R₃₄, and R₃₅ each represent a hydrogen atom, an alkyl group, a substituted amino group or an aryl group; and u represents 0 or
 1. 11. An electrophotographic photoreceptor comprising a conductive support having thereon a light-sensitive layer containing hydroxygallium phthalocyanine crystals having distinct diffraction peaks at degrees of the Bragg angle (2θ±0.2) in the X-ray diffraction spectrum prepared by treating hydroxygallium phthalocyanine with a solvent selected from the group consisting of amides, ketones, alcohols, amines, aromatic alcohols and polyhydric alcohols and a benzidine compound represented by formula (II): ##STR35## wherein R₅ represents a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom; R₆ and R₇ each represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, or a substituted amino group; and p and q each represents 0, 1 or 2, or a tetraaryl-m-phenylenediamine compound represented by formula (III): ##STR36## wherein R₈, R₉, and R₁₀ each represents a hydrogen atom, an alkyl group, an alkoxy group, a substituted or unsubstituted aryl group or an aralkyl group, as a charge transporting material.
 12. An electrophotographic photoreceptor as claimed in claim 11, having distinct diffraction peaks at 7.5°, 9.9°, 12.5°, 16.3°, 18.6, 25.1° and 28.3° of the Bragg angle (2θ±0.2) in the X-ray diffraction spectrum.
 13. An electrophotographic photoreceptor as claimed in 11, having distinct diffraction peaks at 7.7°, 16.5°, 25.1° and 26.6° of the Bragg angle (2θ±0.2) in the X-ray diffraction spectrum.
 14. An electrophotographic photoreceptor as claimed in 11, having distinct diffraction peaks at 7.9°, 16.5°, 24.4° and 27.6° of the Bragg angle (2θ±0.2) in the X-ray diffraction spectrum.
 15. An electrophotographic photoreceptor as claimed in 11, having distinct diffraction peaks at 7.0°, 7.5°, 10.5°, 11.7°, 12.7°, 17.3°, 18.1°, 24.5°, 26.2° and 27.1° of the Bragg angle (2θ±0.2) in the X-ray diffraction spectrum.
 16. An electrophotographic photoreceptor as claimed in 11, having distinct diffraction peaks at 6.8°, 12.8°, 15.8° and 26.0° of the Bragg angle (2θ±0.2) in the X-ray diffraction spectrum.
 17. An electrophotographic photoreceptor as claimed in 11, having distinct diffraction peaks at 7.4°, 9.9°, 25.0° and 28.2° of the Bragg angle (2θ±0.2) in the X-ray diffraction spectrum prepared by treating hydroxygallium phthalocyanine with a solvent selected from the group consisting of amides, esters and ketones.
 18. An electrophotographic photoreceptor as caliemd in claim 11, wherein said benzidine compound represented by formula (II) is a compound represented by formula (IV): ##STR37## wherein R₁₁ and R₁₂ each represent a hydrogen atom or a methyl group.
 19. An electrophotographic photoreceptor as claimed in claim 11, wherein said benzidine compound represented by formula (II) is a compound represented by formula (V): ##STR38## wherein either one of R₁₃ and R₁₄ represents an alkyl group having 2 or more carbon atoms, with the other representing a hydrogen atom, an alkyl group, an alkoxy group or a substituted amino group.
 20. An electrophotographic photoreceptor comprising a conductive supporting having thereon a light-sensitive layer, said light-sensitive layer containing hydroxygallium phthalocyanine crystals having distinct diffraction peaks at degrees of the Bragg angle (2θ±0.2) in the X-ray diffraction spectrum prepared by treating hydroxygallium phthalocyanine with a solvent selected from the group consisting of amides, ketones, alcohols, amines, aromatic alcohols and polyhydric alcohols and a benzidine compound represented by formula (XVII), (XVIII), (XIX) or (XX) as a charge transporting material: ##STR39## wherein R₂₃ and R₂₄ each represents a hydrogen atom, an alkyl group or an aryl group; Y represents --(C(CH₃)₂)--, --(CH₂)_(t) --, wherein t represents an integer of from 1 to 5, --(OCH₂ CH₂)_(t), wherein t represents an integer of from 1 to 5, --CH═CH--, --CO(CH₂)₂, --CO(CH₂)₃ --, a cyclobenzylidene group or a cyclohexylidene group; ##STR40## wherein R₂₅, R₂₆, and R₂₇ each represents a hydrogen atom, an alkyl group, a substituted or unsubstituted aryl group or an aralkyl group; ##STR41## wherein R₂₈ and R₂₉ each represents a hydrogen atom, a halogen atom, an alkyl group or a substituted or unsubstituted aryl group; and R₃₀ and R₃₁ each represents a hydrogen atom, an alkyl group or a substituted or unsubstituted aryl group, or R₃₀ and R₃₁ are taken together to form an atomic group forming a condensed carbon ring; ##STR42## wherein R₃₂, R₃₃, R₃₄ and R₃₅ each represents a hydrogen atom, an alkyl group, a substituted amino group or an aryl group; and u represents 0 or
 1. 